A Clinical Approach to Acute Renal Failure A Clinical Approach to Acute Renal Failure

Jeffrey J. Kaufhold, MD FACP

May 2010

Summary

• Causes of Acute Renal Failure– Differential– Pre-Renal– Intra-renal– Post-Renal

• Initial treatment of ARF• Cases to review

Reason for Nephrology Consultation

Reason for Nephrology Consultation

ARF

Fluid & Lytes

Other

60%60%

15%15%

25%25%

Ref: Paller Sem Neph 1998, 18(5), 524.Ref: Paller Sem Neph 1998, 18(5), 524.

Approach to ARF

• Pseudo-ARF

• Pre-Renal

• Intra-Renal

• Post- Renal

Approach to ARF

• Pseudo-ARF– Pt hosp for liver lac, allowed to go home on

weekends. Normal renal function.– First weekend, creat bumped to 1.5, not noticed– 2nd weekend, creat up to 1.8, hydrated and came

down.– 3rd weekend, creat over 2.0, so we were

consulted.– What was happening?

Approach to ARF

• Pseudo-ARF– Pt was eating steak dinners at

home/restaurant– Texan so steak was WELL done– Creatine in muscle converted to Creatinine.

• Creatinine production also much higher in Rhabdomyolysis, so BUN / Creat ratio may be less than 10.

Approach to ARF

• Pre-Renal– Most common– Due to NPO, Diuretics, ACE inhibitors,

NSAIDS– Due to renal artery disease, CHF with poor

EF.– Usually BUN / creat ratio over 20.– Usually creat < 2.5

Approach to ARF

• Intra-Renal– Most commonly pre-renal tipping over into

true renal injury.– Acute Tubular Necrosis is result (70%)– Tubulo-Interstitial Nephritis (20%)– Acute vasculitis/GN rare (5-10 %)

Instigating Factors for ARF in a Referral Hospital

Instigating Factors for ARF in a Referral Hospital

Others

Surgery

Drugs

Cardiac

Infections

Hypovlemia

30%30%

11%11%

12%12%

12%12%30%30%

5%5%

Ref: Paller Sem Neph 1998, 18(5), 524.Ref: Paller Sem Neph 1998, 18(5), 524.

Approach to ARF

• Post- Renal– Most commonly due to obstruction at

bladder outlet• Prostate problems• Neurogenic bladder• Stone• Urethral stricture (esp after CABG)

Distribution of ARF Cause

Distribution of causes: Pre-renal Intra-renal Post-renal CHF ATN (70%) Obstruction @ Nausea/vomiting Interstitial Nephritis (15-20%) Bladder Outlet NPO status Glomerulonephritis (5%) most commonly Medications Vasculitis (1%) (diuretics, ACE, NSAIDS)

Initial Treatment of ARF

• Fluid Resuscitation

• Always place Foley Catheter

• Stop offending agents– NSAIDS, Contrast, ACE/ARB, potassium

• Watch labs

• Consider diuretics/Natrecor

Indications for Dialysis

• A acidosis

• E electrolyte abnormalities

• I intoxication/poisoning

• O fluid overload

• U uremia symptoms/complications

Choice of Dialysis Modality

• Standard Hemodialysis - The gold standard, able to clear the most toxins quickest, requires stable patient

• Acute Peritoneal Dialysis - good for fluid and uremic waste product removal, avoids need for vascular access. Requires a closed abdomen, not good for poisonings

• CVVHD - useful for unstable/hypotensive patients.

ARF Case :Basic 1.

• 57 y.o. male on the surgery service for abdominal pain. Admitted and observed overnite, noted the next morning to have elevated creatinine from 1.5 on admission to 2.1. Urinalysis on admission is negative for blood or protein. Exam confirms abdominal tenderness, possible fullness in suprapubic region without specific mass. Patient denies difficulty voiding, has decent urine output since admission.

• Likely cause of renal failure: • Pre Post Intra - renal?

• What would you do to evaluate First ?

ARF Case: Basic 2

Basic 2: 63 y.o. male admitted with persistent nausea and vomiting, 2 weeks after cardiac cath for chest pain. Creatinine pre-cath was 1.8, no new medications given. Has history of diabetes mellitus and urinalysis shows proteinuria 3+. Your next test would be: a. Upper endoscopy b. CT scan of abdomen c. Basic metabolic profile (lytes BUN, Creat) d. Renal ultrasound.

ARF Case: Basic 3.

Basic 3. 77 y.o. female with no prior history of renal disease admitted with nausea and vomiting for 3 days. Found to have creat of 6.0 on admission lab. Serum bicarb: 15, K+ is 3.8, Na+ is 120. Likely Cause of renal failure: Pre Post Intra? What would your admission orders look like: Diet: IV What fluid, what rate? Nursing issues: How soon do you recheck labs?

ARF Case: Basic 4• 34 y.o. recruiter for the Army admitted with weakness,

confusion, 2 days after his fitness test (required run, pushups, etc.) Admission labs show normal electrolytes but BUN is 38, Creatinine is 8.0. Urinalysis shows 2+ protein, 4 + blood but microscopic doesn’t show much RBC’s, no casts. Likely cause of renal failure: Pre Post Intra?

• What confirmatory test would you order next?• a. CT scan of head• b. CPK with MB’s, troponin• c. ANA, ANCA, renal biopsy• d. Renal ultrasound.

ARF Case: Basic 5

• 49 y.o. diabetic with no prior history of renal disease is admitted with cellulitis of the leg. Started on Unasyn at appropriate dose, creat on admission is 0.9. 2 days into therapy the leg is improving and the creatinine is 1.8. Urinalysis shows 3+ leukocytes, 2 + blood, 1 + glucose, and 2 + protein

• Cause of ARF: Pre Intra Post ?• How would you evaluate this? • How would you treat this?

ARF Case: Advanced 1

• Same story as Basic #1, but the surgeons perform CT scan of the abdomen. The CT shows para-aortic adenopathy with possible colon primary. Hydronephrosis is present bilaterally.

• Potential causes of the renal failure?

• How would you relieve the obstruction?

ARF Case: Advanced 2

• You are called to consult on a Pt in the SICU 2 days post-op with acute renal failure. Had bowel obstruction and after conservative treatment failed, was taken for lysis of adhesions. No ischemic changes were seen. Initially post op he looked OK and was extubated on the first post op day. The night before you were consulted he developed resp failure and was re-intubated. Looking back through the labs, you see that his creatinine was 1.0 pre-op, lytes were fairly normal, but phosphorus was 2.0. Pt had not received TPN during his 9 day hospitalization, but this was started post-op. His labs which prompted your consult show Na+ 128, K+ 5.5, CO2 14, BUN 78, creat 3.1, Phosphorus 6.0.

• Are the lab disturbances due to the TPN?

Advanced Case 2

• Differential for the ARF would include which of the following?• a. Contrast nephropathy• b. ATN from hypotension, surgery, volume depletion.• c. Rhabdomyolysis• d. Sepsis• e. Nephrotoxic antibiotics• f. Hypoxia and poor perfusion due to resp failure• g. Obstruction• h. Allergic interstitial nephritis (AIN)• i. Acute Glomerulonephritis/RPGN• j. Cholesterol Embolism syndrome.